Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$111.27	10.866%	$123.3606	$123.36	$123.35	$123.40
Purchase #2	$230.49	12.323%	$258.8933	$258.89	$258.90	$258.90
Purchase #3	$181.40	9.172%	$198.038	$198.04	$198.05	$198.00
Purchase #4	$205.27	11.873%	$229.6417	$229.64	$229.65	$229.60
Purchase #5	$205.95	4.159%	$214.5155	$214.52	$214.50	$214.50
Purchase #6	$40.61	6.632%	$43.3033	$43.30	$43.30	$43.30
Purchase #7	$188.56	8.644%	$204.8591	$204.86	$204.85	$204.90
7 purchase totals =	$1,163.55		$1,272.6115	$1,272.61	$1,272.60	$1,272.60